Cephalosporin derivatives

ABSTRACT

Novel cephem derivatives represented by the general formula ##STR1## wherein Ar is an optionally substituted lipophilic phenyl, naphthyl, benzthiazolyl or pyridyl group; R 1  represents a group of the formula ##STR2## in which R 8  and R 9  are each independently hydrogen, C 1  -C 6  alkyl or (C 1  -C 6 )alkoxycarbonyl, said C 1  -C 6  alkyl group being optionally substituted by 1-5 hydroxy or C 1  -C 6  alkoxy groups; m is either 0 or 1; A is a C 2  -C 10  alkyl group optionally substituted by 1-5 hydroxy groups; and R 2  and R 3  are each independently hydrogen or C 1  -C 6  alkyl. The derivatives are gram-positive antibacterial agents especially useful in the treatment of diseases caused by methicillin-resistant Staphylococcus aureus.

BACKGROUND OF THE INVENTION

This application claims the benefit of U.S. Provisional Application No. 60/008,940, filed Dec. 20, 1995.

1. Field of the Invention

The present invention is directed to new cephem derivatives represented by the general formula ##STR3## wherein Ar is an optionally substituted lipophilic phenyl, naphthyl, benzthiazolyl or pyridyl group; R¹ represents a group of the formula ##STR4## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl or (C₁ -C₆)alkoxycarbonyl, said C₁ -C₆ alkyl group being optionally substituted by 1-5 hydroxy or C₁ -C₆ alkoxy groups; m is either 0 or 1; A is a C₂ -C₁₀ alkyl group optionally substituted by 1-5 hydroxy groups; and R² and R³ are each independently hydrogen or C₁ -C₆ alkyl. The derivatives are gram-positive antibacterial agents especially useful in the treatment of diseases caused by methicillin-resistant Staphylococcus aureus (also referred to below as MRSA or methicillin-resistant S. aureus).

2. Description of the Prior Art

The literature discloses a vast number of cephem derivatives having a wide variety of C-3 and C-7 substituents. Applicants are not aware, however, of any literature disclosing compounds with the combination of C-3 and C-7 substituents found by applicants to give good activity against MRSA organisms. There are, however, references which disclose cephalosporins having the type of 7-substituents or the type of 3-substituents present in the compounds claimed in the present application.

For example, there are references which disclose applicants' C-7 substituents. Among such references disclosing 7-substituents of the type ##STR5## where Ar is an aromatic group are the following:

U.S. Pat. No. 4,056,676 discloses cephem derivatives of the general formula ##STR6## where Z is hydrogen or fluorine; and when Z is hydrogen, each of X and Y is hydrogen or chlorine selected so that the phenyl ring is substituted with 1 or 2 chlorine atoms and so that when one chlorine atom is present said chlorine atom is in the 3-position, and when two chlorine atoms are present said chlorine atoms are in the 3,4-, the 3,5- or the 2,5-positions; and when Z is fluorine, said fluorine is in the 3- or 4-positions of the phenyl ring and each of X and Y is hydrogen or chlorine selected so that when the phenyl ring is substituted with 1 or 2 chlorine atoms, one of the chlorine atoms is in the 3- or 4-position of the phenyl ring; R¹ is hydrogen, dicyclohexylamine, or a pharmaceutically acceptable cation; and R is, inter alia, N-pyridino. Among the compounds specifically disclosed are those of the formulae: ##STR7## The compounds disclosed are said to be useful for treating and inhibiting the growth of MRSA organisms.

The cephalosporin derivative of the formula ##STR8## is disclosed in Antimicrobial Agents and Chemotherapy-1966, pg. 573-580 at page 576 (Compound No. 48).

J. Antibiotics, 26(12), 737-744, 1973, discloses the compound of the formula ##STR9##

U.K. Patent 998,265 discloses cephem derivatives of the general formula ##STR10## in which R¹, taken alone, is --OH, C₁ -C₈ acyloxy, or tertiaryamino, R² is --OH when R¹ is --OH, R² is --OH when R¹ is C₁ -C₈ acyloxy, R² is --O-- when R¹ is tertiaryamino, R¹ and R², when taken together, are --O--, R³ and R⁴ represent hydrogen, alkyl radicals having from 1 to 6 carbon atoms, alkenyl radicals having from 2 to 6 carbon atoms, cycloalkyl radicals having from 5 to 7 carbon atoms, or alkoxyalkyl radicals having from 2 to 6 carbon atoms; n represents 0 to 4; and R⁵ represents an alkyl radical having from 1 to 6 carbon atoms, an alkenyl or alkynyl radical having from 2 to 6 carbon atoms, a cycloalkyl radical having 5 or 6 carbon atoms, phenyl, β-furyl, β-thienyl, thienyl, or naphthyl, or a fluoro, chloro, bromo, nitro, trifluoromethyl, C₁ -C₄ alkyl, C₁ -C₄ alkylmercapto, or C₁ -C₄ alkoxy substitution product of such radicals.

U.K. Published Application No. 2,007,221 A discloses cephalosporin derivatives of the formula ##STR11## wherein Y is hydrogen, chlorine, bromine, C₁ -C₄ alkyl or C₁ -C₄ alkoxy; Z is a bond, oxygen or sulfur; W is hydrogen, methyl, amino, hydroxy, SO₃ H or COOR₄ wherein R₄ is hydrogen or 5-indanyl with the proviso that when Z is oxygen or sulfur, W is other than hydroxy; R₁ is hydrogen or methoxy; R₂ is hydrogen, acetoxy, 1,3,4-thiadiazol-2-ylthio, 5-methyl-1,3,4-thiadiazol-2-ylthio, tetrazol-5-ylthio, 1-methyltetrazol-5-ylthio, 1,3,4-oxadiazol-2-ylthio, 5-methyl-1,3,4-oxadiazol-2-ylthio, 1,3,4-triazol-2-ylthio, 5-methyl-1,3,4-triazol-2-ylthio, 1,2,3-triazol-5-ylthio, pyridinium or 4-aminocarbonylpyridinium; R₃ is hydrogen, a negative charge when R₂ is pyridinium or 4-aminocarbonylpyridinium, a cation of an alkali metal or an alkaline earth metal, ammonium or organic ammonium cations, C₁ -C₄ alkyl, (C₂ -C₅ alkanoyloxy)methyl, (C₂ -C₅) alkanoylamino)methyl, C₂ -C₅ alkanoyl(C₁ -C₄ alkoxy)carbonyl(C₁ -C₄ alkyl)-amino-methyl, p-(C₂ -alkanoyloxy)benzylamino(C₂ -C₁₅ alkanoyloxy)methyl, (C₁ -C₄ alkyl)amino(C₂ -C₁₅ alkanoyloxy)methyl or di(C₁ -C₄ alkyl)amino(C₂ -C₁₅ alkanoyloxy)methyl; and pharmaceutically acceptable salts thereof.

U.S. Pat. No. 3,217,000 discloses cephem derivatives of the formula ##STR12## wherein Thi is 2-thienyl or 3-thienyl and R is a substituent at the 3 or 4 position of the pyridino ring selected from the group consisting of cyano, carboxy, carbamyl, N-methylcarbamyl, carbo(C₁ -C₄ alkoxy), hydroxy and (C₁ -C₄)alkanoyl; and the salts thereof with pharmaceutically acceptable acids.

There is also literature disclosing cephalosporins having 3-substituents of the type ##STR13## where R is an optionally substituted aliphatic group. Among such references are those of the following:

Published European Patent Application 248,645 A2 discloses cephalosporin derivatives of the formula ##STR14## wherein R¹ is an optionally protected amino group, R² is a substituted or unsubstituted hetereocyclic group having 1 to 3 hetero atoms selected from the group consisting of nitrogen and sulfur, and R³ is an optionally protected carboxyl group. Among possible R² groups is the group ##STR15## where R⁴ may be lower alkyl substituted by cyano, hydroxyl, lower alkoxy, N-(lower alkyl)carbamoyloxy, carboxyl, amino, N,N-di(lower alkyl)amino, acylamino, N-(lower alkyl)carbamoyl)amino, N-(lower alkyl)thio-carbamoylamino, (lower alkoxy)carbonylamino, (lower alkyl)thio, phenyl, carbamoylphenyl, 2-(lower alkyl)-1,3,4-thiadiazol-5-yl and ##STR16## where R^(a) and R^(b) are the same or different and each represent hydrogen, lower alkyl, hydroxyl, amino or lower alkenyl, or R^(a) and R^(b) taken together with the nitrogen atom to which they are attached may form morpholino and Z is oxygen or sulfur. Included within the disclosure are compounds such as ##STR17## where R² is ##STR18##

Published European Patent Application 209,751 A2 discloses cephalosporin derivatives of the formula ##STR19## where A may represent a group of the formula ##STR20## wherein n is O or an integer of 3-5; R¹ and R² may be the same or different and each represent a hydrogen atom, a halogen atom, a carboxyl group or an optionally halogen-substituted lower alkyl group having 1-5 carbon atoms; and R³ may inter alia represent --(CH₂)_(m) --B where m is an integer of 0-3 and B represents a hydroxyl group, an alkoxy group, an amino group, an alkyl-substituted amino group, a carboxyl group, a carbamoyl group, a sulfonic acid group, a sulfonic acid amide group, a hydroxamic acid group, a cyano group, a thiol group, an alkylthio group, a methanesulfonyl-aminocarbonyl group or an acetamidosulfonyl group.

Published European Patent Application 190,900 A2 discloses cephalosporin compounds of the formula ##STR21## wherein R¹ represents a lower alkyl group which is unsubstituted or substituted by a cyano group or a halogen atom, R² represents a hydroxy lower alkyl group, a cyano group, a lower alkylthio group, a lower alkenyl group substitutable by carboxy, a lower alkinyl group, an imidazolyl group, a C₃ -C₆ alicyclic group, a 2-oxo-1,3-dioxol-5-yl group, a 2-carboxy-1,3-dithiolan-2-yl group, --COR^(A) wherein R^(A) is an amino group, a pyridyl group, a carboxyl group, a C₃ to C₆ alicyclic group, a lower alkyl group which is unsubstituted or substituted by a halogen atom, or ##STR22## wherein R⁸ represents a lower alkyl group which is unsubstituted or substituted by a carboxyl group, R^(c) represents a carboxyl group or a lower alkyl group, n represents an integer of 1 to 3; R³ represents a hydrogen atom or a lower alkyl group.

Japanese Kokai JP 5,148,272A discloses cephalosporin derivatives of the type ##STR23## wherein R is optionally substituted alkyl, alkenyl, cycloalkyl or amino; R¹ and R³ are H, an ester forming group or a salt forming group; R² is optionally protected amino and n is O or 1.

Japanese Kokai JO 2,306,979A discloses cephalosporin derivatives of the formula ##STR24## wherein R₁ is lower alkyl, carbamoyl lower alkyl, carboxy lower alkyl, halogen-substituted lower alkyl, lower alkenyl or cycloalkyl; R₂ is hydrogen or lower alkyl; and R₃ is hydroxy, lower alkoxy, carbamoyl optionally substituted by lower alkyl, sulfamoyl, amino, carbamoylamino, acylamino, carboxyphenyl or 5- or 6-membered heterocycle containing one or two hetero atoms selected from O, N and S.

Japanese Kokai JO 2,215,788A discloses cephalosporin derivatives of the formula ##STR25## wherein R¹ is hydrogen, lower alkyl or --CR⁴ R⁵ --COOH; R² and R³ are hydrogen or lower alkyl; and R⁴ and R⁵ are hydrogen, lower alkyl, phenyl or 3,4-dihydroxyphenyl, or together form ═CH₂.

Japanese Kokai JO 1,146,822A discloses cephalosporin derivatives of the formula ##STR26## wherein R¹ is lower alkenyl, pyridyl or oxopyrrolidinyl; or R¹ may be lower alkyl which may be substituted by CN, amino, OH, lower alkylthio, lower alkoxy, phenyl carbamoylphenyl, 2-lower alkyl-1,3,4-thiadiazol-5-yl, or --C(═Z)--NH--R⁴ ; R² and R³ ═H, lower alkyl or carbamoyl; R⁴ is hydrogen, lower alkyl or OH; and Z is O or S.

Japanese Kokai J 62,238,290A discloses cephalosporin derivatives of the formula ##STR27## wherein R¹ is lower alkyl, cyclopropyl, cyclopropylmethyl or --(CH₂)_(n) A; n=0-3; A is OH, alkoxy, halogen, amino, alkylamino, COOH, carbamoyl, hydroxamic acid, sulfonic acid or sulfonamido; and R² and R³ are H or lower alkyl.

Published European Patent Application 69,872 A2 discloses cephalosporin derivatives of the formula ##STR28## wherein R¹ is amino or protected amino; R² is hydrogen, lower aliphatic hydrocarbon group which may be substituted with suitable substituents, cyclo(lower)alkyl or cyclo(lower)alkenyl; R³ is lower alkyl which may be substituted with suitable substituents; R^(3a) is hydrogen, lower alkyl or amino; and R^(3b) may be hydrogen or lower alkyl. The R³ lower alkyl group may be substituted by carboxy, protected carboxy, hydroxy, amino, protected amino, carbamoyl and the like.

U.S. Pat. No. 4,315,005 discloses cephalosporin derivatives of the formula ##STR29## wherein R^(a) and R^(b) represent C₁ -C₂ alkyl or, together with the carbon atom to which they are attached, form a C₃ -C₆ cycloalkylidene group and Y represents ##STR30##

SUMMARY OF THE INVENTION

The present invention provides a novel series of cephem derivatives of the general formula ##STR31## wherein Ar is a group selected from ##STR32## in which R⁴, R⁵ and R⁶ are each independently hydrogen, halogen, trihalomethyl, amino, hydroxy, hydroxy(C₁ -C₆)alkyl, C₁ -C₆ alkyl, --(CH₂)_(n) OR⁷ or --(CH₂)_(n) SR⁷ ; n is an integer of from 1 to 6; R⁷ is hydrogen or C₁ -C₆ alkyl; R¹ represents a group of the formula ##STR33## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl or (C₁ -C₆)alkoxycarbonyl, said C₁ -C₆ group being optionally substituted by one or more hydroxy or C₁ -C₆ alkoxy groups; m is either 0 or 1; A is a C₂ -C₁₀ alkyl group optionally substituted by 1 to 5 hydroxy groups; a R² and R³ are each independently hydrogen or C₁ -C₆ alkyl; and R¹⁰ is hydrogen, an anionic charge or a carboxyl-protecting group, provided that when R¹⁰ is hydrogen or a protecting group, there is also present a counter ion; or a pharmaceutically acceptable salt or prodrug thereof.

The compounds of formula I are antibacterial agents useful in the treatment of infections in humans and other animals caused by a variety of gram-positive bacteria, particularly methicillin-resistant S. aureus.

Also included in the invention are processes for preparing the compounds of formula I and pharmaceutical compositions containing said compounds in combination with pharmaceutically acceptable carriers or diluents.

DETAILED DESCRIPTION

The present invention provides novel cephem derivatives of general formula I above which are antibacterial agents useful in the treatment of infectious diseases in humans and other animals. The compounds exhibit good activity against a variety of gram-positive microorganisms, e.g. S. pneumoniae, S. pyogenes, S. aureus, E. faecalis, E. faecium, S. epidermidis and S. hemolyticus, and are particularly useful against strains of methicillin-resistant S. aureus.

The compounds of formula I are characterized by a substituted pyridiniumthiomethyl group of the type ##STR34## at the 3-position of the cephem ring and a lipophilic 7-substituent of the type ##STR35## wherein Ar is an aromatic group selected from optionally substituted phenyl, naphthyl, benzthiazolyl or pyridyl.

To elaborate on the definitions for the substituents of the formula I compounds:

(a) "Halogen" includes chloro, bromo, fluoro and iodo, and is preferably chloro or bromo;

(b) "Trihalomethyl" includes trichloromethyl, trifluoromethyl, tribromomethyl and triiodomethyl, but is preferably trifluoromethyl;

(c) The aliphatic "alkyl" and "alkoxy" groups may be straight or branched chains having the specified number of carbon atoms, e.g. in the case of C₁ -C₆ alkyl, the alkyl group may have from 1 to 6 carbon atoms. It is preferred that such groups have up to 4 carbon atoms.

The term "pharmaceutically acceptable salt" as used herein is intended to include the nontoxic acid addition salts with inorganic or organic acids, e.g. salts with acids such as hydrochloric, phosphoric, sulfuric, maleic, acetic, citric, succinic, benzoic, fumaric, mandelic, p-toluene-sulfonic, methanesulfonic, ascorbic, lactic, gluconic, trifluoroacetic, hydroiodic, hydrobromic, and the like. Some of the compounds of the present invention have an acidic hydrogen and can, therefore, be converted with bases in a conventional manner into pharmaceutically acceptable salts. Such salts, e.g. ammonium, alkali metal salts, particularly sodium or potassium, alkaline earth metal salts, particularly calcium or magnesium, and salts with suitable organic bases such as lower alkylamines (methylamine, ethylamine, cyclohexylamine, and the like) or with substituted lower alkylamines (e.g. hydroxyl-substituted alkylamines such as diethanolamine, triethanolamine or tris(hydroxymethyl)-aminomethane), or with bases such as piperidine or morpholine, are also intended to be encompassed by the term "pharmaceutically acceptable salt".

Compounds of formula I in the form of acid addition salts may be written as ##STR36## where x.sup.⊖ represents the acid anion and R¹⁰ is hydrogen or a carboxyl-protecting group. The counter anion x.sup.⊖ may be selected so as to provide pharmaceutically acceptable salts for therapeutic administration.

The carboxyl-protecting group R¹⁰ is intended to include readily removable ester groups which have been employed to block a carboxyl group during the reaction steps used to prepare compounds I and which can be removed by methods which do not result in any appreciable destruction of the remaining portion of the molecule, e.g. by chemical or enzymatic hydrolysis, treatment with chemical reducing agents under mild conditions, irradiation with ultraviolet light or catalytic hydrogenation, etc. Examples of such protecting groups include benzhydryl, p-nitrobenzyl, 2-naphthylmethyl, allyl, benzyl, p-methoxybenzyl, trichloroethyl, silyl such as trimethylsilyl, phenacyl, acetonyl, o-nitrobenzyl, 4-pyridylmethyl and C₁ -C₆ alkyl such as methyl, ethyl or t-butyl. Included within such protecting groups are those which are hydrolyzed under physiological conditions such as pivaloyloxymethyl, acetoxymethyl, phthalidyl, indanyl, α-acetoxyethyl, α-pivaloyloxyethyl, and methoxymethyl. Compounds of formula I with such physiologically hydrolyzable carboxyl protecting groups are also referred to herein and in the claims as "prodrugs" . Compounds of formula I where R¹⁰ is a physiologically removable protecting group are useful directly as antibacterial agents. Compounds where an R¹⁰ protecting group is not physiologically removable are useful intermediates which can be easily converted to the active form by conventional deblocking procedures well-known to those skilled in the art.

Compounds of formula I wherein a hydroxyl substituent is esterified with a group hydrolyzable under physiological conditions are also included within the scope of the term "prodrug" as used herein and in the claims. Such hydroxyl protecting groups may be employed, for example, to increase the solubility of the formula I compound. Illustrative of suitable ester "prodrugs" of this type are compounds of formula I wherein one or more hydroxy substituent groups are converted to sulfate (--OSO₃ H) or phosphate (--OPO₃ H₂) groups.

A preferred embodiment of the present invention comprises compounds of formula I wherein R¹ is ##STR37## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl, hydroxy(C₁ -C₆)alkyl or (C₁ -C₆)alkoxycarbonyl and A is a C₂ -C₁₀ alkyl groups optionally substituted by 1-5 (preferably 1 or 2 and most preferably 1) hydroxy groups.

Specific preferred R₁ groups include: ##STR38## where t-Bu represents tertiary butoyl.

Preferred Ar groups are those of the formulae ##STR39## in which R⁴, R⁵ and R⁶ are each independently hydrogen, C₁ -C₆ alkyl, halogen, trifluoromethyl, hydroxy or hydroxy(C₁ -C₆ alkyl).

Another preferred embodiment of the present invention comprises compounds of formula I wherein Ar is a group selected from ##STR40## in which R⁴, R⁵ and R⁶ are each independently hydrogen, halogen, trihalomethyl, amino, hydroxy, hydroxy(C₁ -C₆)alkyl, C₁ -C₆ alkyl, --(CH₂)_(n) OR⁷ or --(CH₂)_(n) SR⁷ ; n is an integer of from 1 to 6; R⁷ is hydrogen or C₁ -C₆ alkyl; R¹ represents a group of the formula ##STR41## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl or (C₁ -C₆)alkoxycarbonyl, said C₁ -C₆ alkyl group being unsubstituted or substituted by 1 or 2 hydroxy or C₁ -C₆ alkoxy groups; A is a C₂ -C₁₀ alkyl group or a C₂ -C₁₀ alkyl group substituted by 1-5 (preferably 1 or 2 and most preferably 1) hydroxy groups; R² and R³ are each independently hydrogen or C₁ -C₆ alkyl; and R¹⁰ is hydrogen, an anionic charge or a carboxyl-protecting group, provided that when R¹⁰ is hydrogen or a protecting group, there is also present a counter ion; or a pharmaceutically acceptable salt or prodrug thereof.

Within the above group, preferred R¹ substituents are ##STR42##

in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl, hydroxy(C₁ -C₆)alkyl or (C₁ -C₆)alkoxycarbonyl. Specific preferred embodiments of such R¹ substituents include ##STR43##

The preferred Ar substituents for the above group are ##STR44## in which R⁴, R⁵ and R⁶ are each independently hydrogen, C₁ -C⁶ alkyl, halogen, trifluoromethyl, hydroxy or hydroxy(C₁ -C₆)alkyl.

The preferred individual compounds of the present invention, all of which have an MIC vs a representative MRSA strain of ≦8 μg/ml, are listed below:

1- Piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 1)

1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 2)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 3)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 4)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (3-bromophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 5)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 6)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-benzthiazolylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 7)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dimethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 8)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-bromopyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 9)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 10)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 11)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 12)

1- N-(3-amino-2-hydroxy-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 13)

1- N-(3-amino-2-hydroxy-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 14)

1- piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 15)

1- N-(2-guanidinyl-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 16)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 17)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 18)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 19)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 20)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 21)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 22)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 23)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 24)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-hydroxymethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 25)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-(2-hydroxy-1-ethyl)phenylthio))acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 26)

1-(3-amino-1-propyl)-2,6-dimethyl-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 27)

1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 28)

1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 29)

1- 3-methylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 30)

1- 3-(2-hydroxyethyl)-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 31)

1- 3-dimethylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 32)

1- 2-(N-morpholinyl)-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 33)

1- 3-(N-morpholinyl)-2-hydroxy-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7-2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 34)

1- 4-amino-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 35)

1- 4-(t-butoxycarbonylamino)-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 36)

1-(2-guanidinyl-1-ethyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 37); and

1-(4-guanidinyl-1-butyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 38).

The more preferred individual compounds of the present invention, all of which have an MIC≦8 μg/ml and a PD₅₀ ≦5 mg/kg against a representative MRSA strain, are listed below:

1- Piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 1)

1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 2)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 3)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 4)

1- N-(2-amino-1-ethyl) carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (3-bromophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 5)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 6)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dimethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 8)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-bromopyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 9)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 10)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 11)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 12)

1- N-(3-amino-2-hydroxy-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 13)

1- piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 15)

1- N-(2-guanidinyl-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 16)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 17)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 18)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 19)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 20)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 21)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 22)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 23)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 24)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-hydroxymethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 25)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4- (2-hydroxy-1-ethyl)phenylthio))acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 26)

1-(3-amino-1-propyl)-2,6-dimethyl-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 27)

1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 28)

1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 29)

1- 3-(2-hydroxyethyl)-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 31).

1- 3-dimethylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 32)

1- 4-amino-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 35)

1- 4-(t-butoxycarbonylamino)-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 36)

1-(2-guanidinyl-1-ethyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 37); and

1-(4-guanidinyl-1-butyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (a compound of Example 38)

The most preferred individual compounds of the present invention are listed below:

1- Piperazinylcarbonylmethyl!-4- (6R)- trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 1)

1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 2)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 3)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 4)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (3-bromophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 5)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dimethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 8)

1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-bromopyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 9)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-S-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 10)

1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium tuner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 12)

piperazinylcarbonylmethyl!-4- (6 R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 15)

1- N-(2-guanidinyl-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 16)

1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 18)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 21)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 22)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 23)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 24)

1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-hydroxymethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 25)

1-(3-amino-1-propyl)-2,6-dimethyl-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 27)

1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 28)

1- 3-dimethylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 32)

1- 4-amino-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 35)

1- 4-(t-butoxycarbonylamino)-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 36)

1-(2-guanidinyl-1-ethyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 37); and

1-(4-guanidinyl-1-butyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof (compound of Example 38).

The compounds of the present invention can be made by conventional methods. Two suitable procedures are summarized by the following reaction scheme: ##STR45##

To elaborate on the above process, thiol VII is converted into the arylthioacetic acid derivative VI by treatment with bromoacetic acid under basic conditions (e.g. aqueous sodium or potassium hydroxide). The reaction temperature for this step is typically between 20° C. and 100° C. Starting thiol VII is commercially available or can be prepared according to known literature procedures. Following acidification of the reaction mixture, the product VI is typically isolated by crystallization or, if necessary, it can be purified by chromatography.

Arylthioacetic acid VI is then coupled with a suitable cephem intermediate having a 3-substituent leaving group. For example, the leaving group may be acetoxy or halo. In the preferred embodiment illustrated by the reaction scheme, the cephem intermediate is the 3-chloro cephem V, but other suitable cephem intermediates with equivalent leaving groups at the 3-position could also be employed. The cephem intermediate V may be acylated with VI or a reactive derivative thereof by conventional acylation procedures well-known in the cephalosporin art to give N-acylated intermediate IV. In addition to using the free arylthioacetic acid, e.g. with a suitable condensing agent such as dicyclohexylcarbodiimide, acylating agent VI may also be employed in the form of equivalent acylating derivatives such as an acid anhydride, mixed anhydride, activated ester, or acid halide. The cephem intermediate preferably has the carboxyl group protected by a conventional carboxyl-protecting group which can be readily removed. Examples of such protecting groups are discussed above and include benzyl, 4-nitrobenzyl, 4-methoxybenzyl, diphenylmethyl, allyl, and the like. Other examples of suitable protecting groups are disclosed in Protective Groups in Organic Synthesis, Theodora W. Greene (John Wiley & Sons, 1981), Chapter 5. In one embodiment, intermediate V may be acylated with acid VI in the presence of dicyclohexylcarbodiimide and in an inert solvent such as tetrahydrofuran or dichloromethane. The reaction temperature is typically between -20° C. and 50° C. Upon completion of the reaction, insoluble material is removed by filtration, the filtrate is concentrated, and the residue is treated with a relatively non-polar solvent such as diethyl ether or ethyl acetate resulting in precipitation of the desired product. Alternatively, acid VI may be converted to the corresponding acid chloride, for example by treatment with thionyl chloride with or without a solvent such as dichloromethane, followed by coupling with cephem amine V in the presence of a base such as triethylamine or N-methylmorpholine to give intermediate IV. Cephem IV is typically isolated after aqueous work-up and evaporation of volatile solvents followed by trituration of the compound with a relatively non-polar solvent such as diethyl ether or ethyl acetate. This intermediate may be used in the next reaction step as the X=chloride derivative, or can be converted to the X=bromide or X=iodide derivative by treatment with the appropriate metal halide in a solvent such as acetone.

Conversion of cephem IV to the target quaternary cephems I is accomplished by two different methods. One method for preparation of I entails displacement of an appropriate 3-substituent leaving group with 4-mercaptopyridine followed by quaternization of the pyridyl nitrogen, and then deprotection of the cephem carboxylate ester. For example, cephem IV (X=Cl) is treated with optionally substituted 4-mercaptopyridine and sodium iodide in a one-pot reaction to give intermediate II. Reaction of thiopyridyl derivative II with a reactive alkylating agent provides the quaternary cephem intermediate I'. Examples of alkylating agents are α-halocarbonyl derivatives such as N-substituted haloacetamides. The alkylation reaction is carried out in an inert solvent such as acetone, dimethylformamide, or tetrahydrofuran and is run at temperatures between -20° C. and 100° C. Removal of the cephem carboxylate ester protecting group to give I is then accomplished under acidic conditions. For example, when R is diphenylmethyl or 4-methoxybenzyl, I is obtained upon treatment of I' with trifluoroacetic acid neat or in an inert solvent such as methylene chloride. A reagent such as anisole may also be employed to scavenge the liberated ester protecting group. The reaction temperature is usually at or below room temperature. The deprotection may also be carried out by treatment with other protic acids such as hydrochloric acid in a solvent such as methanol. The final product is typically isolated by precipitation or crystallization. In some cases, cephem I is purified by column chromatography, for example on reversed-phase adsorbent.

In a second method of preparing quaternary cephems I, intermediate IV is deprotected under acidic conditions, followed by reaction of the resulting intermediate IV' with a thiopyridone derivative III. For example, when R is diphenylmethyl or 4-methoxybenzyl, cephem acid IV' is obtained upon treatment of IV with trifluoroacetic acid neat or in an inert solvent such as methylene chloride. A reagent such as anisole may also be employed to scavenge the liberated ester protecting group. The reaction temperature is usually at or below room temperature. The deprotection may also be carried out by treatment with other protic acids such as hydrochloric acid in a solvent such as methanol. The final product is typically isolated by precipitation or crystallization. Reaction of IV' with a thiopyridone derivative III in a solvent such as dimethylformamide, dimethyl sulfoxide, ethanol, methanol, or other appropriate solvents at a temperature between -20° C. and 100° C. affords target quaternary cephem I. The final product is isolated as described above. Thiopyridones III are typically prepared according to a method analogous to that described in T. Takahashi et al., European Patent Application No. 209751 and in I. E. El-Kholy et al., J. Heterocyclic Chem. Vol. 11, p. 487 (1974). This procedure entails reaction of 4-thiopyrone (European Patent No. 209751) with an appropriate primary amine in a solvent such as aqueous methanol or ethanol at a temperature ranging between 0° C. and 78° C. The primary amine may be in the form of a zwitterion in examples where there is a free acid group present in the molecule. In these cases, a base such as sodium hydroxide, sodium bicarbonate, or pyridine is added to form the free amine in situ. The product may be isolated as its sodium salt by evaporation of volatile solvents, followed by trituration with a solvent such as diethyl ether or ethyl acetate. Alternatively, the reaction mixture may be acidified and extracted with an organic solvent to afford the product as the free carboxylic acid. If the carboxylate group is protected as an ester, the amine may be free or present as an acid salt. In the latter case, a base such as sodium hydroxide, sodium bicarbonate, or pyridine is added to form the free amine in situ. The product is typically isolated by precipitation or by reversed phase column chromatography following removal of volatile solvents.

It will be understood that where the substituent groups used in the above reactions contain certain reaction-sensitive functional groups such as amino or carboxylate groups which might result in undesirable side-reactions, such groups may be protected by conventional protecting groups known to those skilled in the art. For example, thiopyridone intermediates of formula III may have an amine functional group protected as the t-butyloxycarbamate. Suitable protecting groups and methods for their removal are illustrated, for example, in Protective Groups in Organic Synthesis, Theodora W. Greene (John Wiley & Sons, 1991). It is intended that such "protected" intermediates and end-products are included within the scope of the present disclosure and claims.

The desired end-product of formula I may be recovered either as the zwitterion or in the form of a pharmaceutically acceptable acid addition salt, e.g. by addition of the appropriate acid such as HCl, HI or methane-sulfonic acid to the zwitterion. Compounds of formula I where R¹⁰ is hydrogen or an anionic charge, or a pharmaceutically acceptable salt thereof, may be converted by conventional procedures to a corresponding compound where R¹⁰ is a physiologically hydrolyzable ester group.

It will be appreciated that certain products within the scope of formula I may have a C-3 substituent group which can result in formation of optical isomers. It is intended that the present invention include within its scope all such optical isomers as well as epimeric mixtures thereof, i.e. R- or S- or racemic forms.

The novel cephalosporin derivatives of general formula I wherein R¹⁰ is hydrogen, an anionic charge or a physiologically hydrolyzable carboxyl-protecting group, or the pharmaceutically acceptable salts or prodrugs thereof, are potent antibiotics active against many gram-positive bacteria. While they may be used, for example, as animal feed additives for promotion of growth, as preservatives for food, as bactericides in industrial applications, for example in waterbased paint and in the white water of paper mills to inhibit the growth of harmful bacteria, and as disinfectants for destroying or inhibiting the growth of harmful bacteria on medical and dental equipment, they are especially useful in the treatment of infectious disease in humans and other animals caused by the gram-positive bacteria sensitive to the new derivatives. Because of their excellent activity against MRSA organisms, they are particularly useful in the treatment of infections resulting from such bacteria.

The pharmaceutically active compounds of this invention may be used alone or formulated as pharmaceutical compositions comprising, in addition to the active cephem ingredient, a pharmaceutically acceptable carrier or diluent. The compounds may be administered by a variety of means, for example, orally, topically or parenterally (intravenous or intramuscular injection). The pharmaceutical compositions may be in solid form such as capsules, tablets, powders, etc. or in liquid form such as solutions, suspensions or emulsions. Compositions for injection, the preferred route of delivery, may be prepared in unit dose form in ampules or in multidose containers and may contain additives such as suspending, stabilizing and dispersing agents. The compositions may be in ready-to-use form or in powder form for reconstitution at the time of delivery with a suitable vehicle such as sterile water.

The dosage to be administered depends, to a large extent, on the particular compound being used, the particular composition formulated, the route of administration, the nature and condition of the host and the particular situs and organism being treated. Selection of the particular preferred dosage and route of application, then, is left to the discretion of the physician or veterinarian. In general, however, the compounds may be administered parenterally or orally to mammalian hosts in an amount of from about 50 mg/day to about 20 g/day. Administration is generally carried out in divided doses, e.g., three to four times a day, analogous to dosing with a cephalosporin such as cefotaxime.

IN VITRO ACTIVITY

Samples of the compounds prepared below in Examples 1-38 after solution in water and dilution with Nutrient Broth were found to exhibit the following ranges of Minimum Inhibitory Concentrations (MIC) versus the indicated microorganisms as determined by tube dilution. The MICs were determined using a broth micro dilution assay in accordance with that recommended by the National Committee for Clinical Laboratory Standards (NCCLS). Mueller-Hinton medium was used except for Streptococci which was tested in Todd Hewitt broth. The final bacterial inoculate contained approximately 5×10⁵ cfu/ml and the plates were incubated at 35° C. for 18 hours in ambient air (Streptococci in 5% CO₂). The MIC was defined as the lowest drug concentration that prevented visible growth.

    ______________________________________                                         Microorganism           MIC range in ug/ml                                     ______________________________________                                         S. aureus methicillin resistant A27223                                                                 0.125-4                                                S. pneumoniae A9585     0.0005-0.015                                           S. pyogenes A9604       0.0005-0.015                                           E. faecalis A20688      0.06-8                                                 E. faecium A24885       0.25-8                                                 S. aureus A9537, penicillinase negative                                                                0.001-0.03                                             S. aureus A15090, penicillinase positive                                                               0.015-0.5                                              S. epidermidis A24548   0.001-0.5                                              S. epidermidis A25783, methicillin resistant                                                           0.03-0.5                                               S. hemolyticus A21638   0.001-2                                                S. hemolyticus A27235, methicillin resistant                                                           0.06-4                                                 ______________________________________                                    

IN VIVO ACTIVITY

The in vivo therapeutic efficacy of the compounds prepared in Examples 1-38 below after intramuscular injection to mice experimentally infected with the representative MRSA strain A27223 was also measured.

The Determination of the Effectiveness of Antimicrobial Agents in Staphylococcus aureus Systemic Infection in Mice

Organisms

The test organism, MRSA strain A27223 used to generate systemic infection in mice, is grown on two large Brain Heart Infusion Agar plates. On each plate, 0.5 ml of frozen stock culture is plated out. Plates are then incubated for 18 hours at 30° C. The next day each plate is washed with 20 ml of Brain Heart Infusion Broth and then pooled together. A microscopic direct count of microorganism is done using a 1:1000 dilution of plate wash. After a direct count is obtained, the number of organisms per milliliter is calculated. The count is adjusted to the desired amount of inoculum by diluting in 4% hog mucin. The desired challenge (amount of organisms given to mice) is 2.4×10⁸ cfu/0.5 ml/mouse for MRSA strain A27223. The mice are infected intraperitoneally with 0.5 ml of challenge. Ten non-treated infected mice are used as controls.

Mice

Mice used are male ICR mice. The average weight of the animals is from 20 to 26 grams.

Drug-preparation and treatment

Compounds are tested at 4 dose levels, (25, 6.25, 1.56, and 0.39 mg/kg) and prepared in 5% cremophor, unless otherwise specified. Vancomycin is used as the control compound, and is dosed at 6.25, 1.56, 0.39, and 0.098 mg/kg. It is prepared in 0.1M phosphate buffer. There are five infected mice per dose level, and they are treated with 0.2 ml of the test compound, preferably by intramuscular injection. Treatment begins 15 minutes and 2 hours post-infection.

Test duration

A PD₅₀ (the dose of drug given which protects 50% of mice from mortality) runs for 5 days. During this time, mortality of mice are checked every day and deaths are recorded. The cumulative mortality at each dose level is used to calculate a PD₅₀ value for each compound. Surviving mice are sacrificed at the end of day 5 by CO₂ inhalation.

Calculation

Actual calculation of PD₅₀ is performed with a computer program using the Spearman-Karber procedure.

Results

The in vivo efficacy, expressed as the PD₅₀ value, ranged from about 0.8 to 22 mg/kg (for certain compounds, more than one test was carried out; the indicated range is for at least one test result when multiple tests were done).

ILLUSTRATIVE EXAMPLES

The following examples illustrate the invention, but are not intended as a limitation thereof. The abbreviations used in the examples are conventional abbreviations well-known to those skilled in the art. Some of the abbreviations used are as follows:

h=hour(s)

mol=mole(s)

mmol=mmole(s)

g=gram(s)

THF=tetrahydrofuran

L=liter(s)

mL=milliliter(s)

Et₂ O=diethyl ether

EtOAc=ethyl acetate

MeOH=methanol

DMF=dimethylformamide

In the following examples, all temperatures are given in degrees Centigrade. Melting points were determined on an electrothermal apparatus and are not corrected. Proton and carbon-13 nuclear magnetic resonance (¹ H and ¹³ C NMR) spectra were recorded on a Bruker AM-300 or a Varian Gemini 300 spectrometer. All spectra were determined in CDCl₃, DMSO-d₆, CD₃ OD, or D₂ O unless otherwise indicated. Chemical shifts are reported in δ units relative to tetramethylsilane (TMS) or a reference solvent peak and interproton coupling constants are reported in Hertz (Hz). Splitting patterns are designated as follows: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br, broad peak; dd, doublet of doublets; dr, doublet of triplets; and app d, apparent doublet, etc.. Infrared spectra were determined on a Perkin-Elmer 1800 FT-IR spectrometer from 4000 cm⁻¹ to 400 cm⁻¹, calibrated to 1601 cm⁻¹ absorption of a polystyrene film, and are reported in reciprocal centimeters (cm⁻¹). Mass spectra were recorded on a Kratos MS-50 or a Finnegan 4500 instrument utilizing direct chemical ionization (DCI, isobutene), fast atom bombardment (FAB), or electron ion spray (ESI). Ultraviolet spectra were determined on a Hewlett Packard 8452 diode array spectrophotometer in the solvent indicated.

Analytical thin-layer chromatography (TLC) was carried out on precoated silica gel plates (60F-254) and visualized using UV light, iodine vapors, and/or staining by heating with methanolic phosphomolybdic acid. Column chromatography, also referred to as flash chromatography, was performed in a glass column using finely divided silica gel at pressures somewhat above atmospheric pressure with the indicated solvents. Reversed-phase analytical thin-layer chromatography was carried out on precoated reverse phase plates and visualized using UV light or iodine vapors. Reversed-phase column chromatography was performed in a glass column using Baker Octadecyl (C₁₈), 40 μm.

EXAMPLE 1 1- Piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium chloride ##STR46## A. 2,5-Dichlorophenylthioacetic acid

A mixture of 2,5-dichlorothiophenol (10.3 g, 57.5 mmol) and bromoacetic acid (8.03 g, 57.8 mmol) in water (225 mL) was treated with 10N NaOH (13 mL, 130 mmol) and the mixture was heated at 100° C. for 1 h. The reaction mixture was then cooled to 0° C. and acidified to pH 1 with 6N HCl. The product precipitated and was collected by filtration to give 13.0 g (95% yield) of 2,5-dichlorophenylthioacetic acid as white crystals, m.p. 118° C. ¹ H NMR (300 MHz, CDCl₃) δ3.74 (s, 2H), 7.15 (dd, J=2, 9 Hz, 1H), 7.32 (d, J=9 Hz, 1H), 7.36 (d, J=2 Hz, 1H). Anal. Calcd. for C₈ H₆ O₂ SCl₂ : C, 40.53; H, 2.55. Found: C, 40.46; H, 2.64.

B. (6R)-trans-3-Chloromethyl-7- (2,5-dichlorophenyl)thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester

Method a: A solution of 2,5-dichlorophenylthioacetic acid (13.0 g, 54.9 mmol) in methylene chloride (55 mL) and thionyl chloride (10 mL, 137 mmol) was heated at reflux for 3 h. The reaction mixture was allowed to cool to room temperature and was concentrated in vacuo. The residue was evaporated two times from toluene to give 14 g of 2,5-dichlorophenyl-thioacetyl chloride (100% yield) as a slightly colored product which was used in the next step without purification. ¹ H NMR (300 MHz, CDCl₃) δ4.13 (s, 2H), 7.22 (dd, J=2, 9 Hz, 1H), 7.35 (d, J=9 Hz, 1H), 7.39 (d, J=2 Hz, 1H).

(6R)-trans-3-Chloromethyl-7-amino-8-oxo-5-thia-1-azabicyclo- 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester, HCl salt was stirred in a biphasic mixture of EtOAc and saturated NaHCO₃ for 0.5 h. The layers were separated, and the organic solution was dried over anhydrous MgSO₄, filtered, and concentrated to dryness. The free base (9.15 g, 22.0 mmol) was dissolved in THF (200 mL), cooled to 0° C., and treated with N-methylmorpholine (3.34 g, 33.0 mmol) and 2,5-dichlorophenylthioacetyl chloride (6.75 g, 26.4 mmol). The reaction mixture was stirred for 1 h at 0° C., diluted with EtOAc (1000 mL) and washed with water (1000 mL) and brine (100 mL). The organic solution was then dried (MgSO₄) and the solvents were evaporated in vacuo. The residue was stirred with ether (100 mL). The product solidified and was collected by filtration to give 12.0 g (86% yield) of (6R)-trans-3-chloromethyl-7- (2,5-dichlorophenyl)-thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester, m.p. 120° C. ¹ H NMR (300 MHz, CDCl₃) δ3.43 (d, J=18 Hz, 1H), 3.59 (d, J=18 Hz, 1H), 3.69 (d, J=17 Hz, 1H), 3.79 (d, J=17 Hz, 1H), 4.36 (d, J=12 Hz, 1H), 4.41 (d, J=12 Hz, 1H), 4.98 (d, J=5 Hz, 1H), 5.81 (dd, J=5, 9 Hz, 1H), 6.98 (s, 1H), 7.14-7.44 (m, 14H). Anal. Calcd for C₂₉ H₂₃ N₂ O₄ S₂ Cl₃ : C, 54.94; H, 3.66; N, 4.42. Found: C, 55.18; H, 3.84; N, 4.62.

Method b: (6R)-trans-3-Chloromethyl-7-amino-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester, HCl salt (Otsuka, 248 g, 0.55 mol) was treated with NaHCO₃ (56 g, 0.66 mol) in water (1.6 L) at 0° C. The mixture was stirred at 0° C. for 0.5 h and then CH₂ Cl₂ (1.5 L) was added. The biphasic mixture was filtered through Celite and the Celite pad was washed with CH₂ Cl₂ (2 L total). The layers were separated and the organic solution was dried over anhydrous MgSO₄, filtered, and concentrated to a volume of ca. 2 L. The free amine solution was then added to a mixture of 2,5-dichlorothiophenylacetic acid (130 g, 0.55 mol) and dicyclohexyl-carbodiimide (144 g, 0.70 mol) in THF (1 L) at room temperature. The reaction mixture was stirred for 2.5 h and then was filtered through Celite, washing the Celite pad with several portions of acetone. The filtrate was concentrated in vacuo to give a solid mass. The solid was slurried in Et₂ O and then collected by filtration, washing the solid with several portions of Et₂ O. The solid was dried under high vacuum over P₂ O₅ to give 268 g (77% yield) of (6R)-trans-3-chloromethyl-7- (2,5-dichlorophenyl)thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester (see above for analytical data).

C. (6R)-trans-3-(4-Pyridylthiomethyl)-7-(2,5-dichlorophenyl)thioacetamido-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, 4-diphenylmethyl ester

A solution of (6R)-trans-3-chloromethyl-7- (2,5-dichlorophenyl)thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester (6.00 g, 9.46 mmol) in acetone (100 mL) was treated with sodium iodide (4.26 g, 28.4 mmol). The mixture was stirred at 20° C. for 3 h and then condensed under reduced pressure to a volume of 50 mL. The concentrated solution was diluted with EtOAc (200 mL) and washed with ice water (100 mL). The organic solution was washed with saturated NaHSO₄ (20 mL), dried (MgSO₄), and evaporated under reduced pressure. The residue was stirred with ether (30 mL). The product solidified and was collected by filtration to give 6.40 g of (6R)-trans-3-iodomethyl-7- (2,5-dichlorophenyl)-thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester (93% yield) as a buff solid, m.p. 124° C. ¹ H NMR (300 MHz, CDCl₃) δ3.43 (d, J=18 Hz, 1H), 3.69 (d, J=17 Hz, 1H), 3.70 (d, J=18 Hz, 1H), 3.78 (d, J=17 Hz, 1H), 4.27 (d, J=9 Hz, 1H), 4.33 (d, J=9 Hz, 1H), 4.96 (d, J=5 Hz, 1H), 5.75 (dd, J=5, 9 Hz, 1H), 7.00 (s, 1H), 7.20-7.46 (m, 14H). Anal. Calcd. for C₂₉ H₂₃ N₂ O₄ S₂ Cl₂ I: C, 48.01; H, 3.20; N, 3.86. Found: C, 48.00; H, 3.14; N, 3.76.

(6R)-trans-3-Iodomethyl-7- (2,5-dichlorophenyl)thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester (3.00 g, 4.14 mmol) was dissolved in THF (50 mL) at 0° C. and treated with 4-mercaptopyridine (0.504 g, 4.54 mmol). A solution of 2,6-lutidine (0.576 g, 5.38 mmol) in THF (1 mL) was added next, and the reaction mixture was stirred at 0° C. for 0.5 h and then at 20° C. for 1 h. The mixture was diluted with ethyl acetate (500 mL) and the organic solution was washed with water (2×500 mL) and brine (100 mL). The solution was then dried (MgSO₄) and evaporated under reduced pressure to give an oil which was treated with Et₂ O (50 mL) to give a solid. The solid was collected by filtration and purified by column chromatography on silica gel (CH₂ Cl₂ to 30% EtOAc/CH₂ Cl₂) to give 1.50 g of (6R)-trans-3- (4-pyridylthiomethyl!-7- (2,5-dichlorophenyl)-thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester as a tan solid (49% yield), m.p. 122° C. ¹ H NMR (300 MHz, CDCl₃) δ3.37 (d, J=18 Hz, 1H), 3.52 (d, J=18 Hz, 1H), 3.68 (d, J=17 Hz, 1H), 3.76 (d, J=17 Hz, 1H), 3.96 (d, J=13 Hz, 1H), 4.16 (d, J=13 Hz, 1H), 4.93 (d, J=5 Hz, 1H), 5.76 (dd, J=5, 9 Hz, 1H), 6.95-7.42 (m, 16H), 7.49 (d, J=9 Hz, 1H), 8.29 (d, J=6 Hz, 2H). Anal. Calcd. for C₃₄ H₂₇ N₃ O₄ S₃ Cl₂ : C, 57.62; H, 3.84; N, 5.93. Found: C, 57.27;H, 3.68; N, 5.79.

D. 1-(N-t-butoxycarbonyl)piperazinylcarbonylmethyl)l-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3yl!methylthio!pyridinium chloride

(6R)-trans-3-(4-Pyridylthiomethyl)-7- (2,5-dichlorophenyl)-thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, 4-diphenylmethyl ester (0.86 g, 1.2 mmol) was dissolved in DMF (12 mL) and 4-(2-bromoacetyl)-1-(t-butoxycarbonyl)piperazine (0.56 g, 1.8 mmol) was added. The reaction mixture was allowed to stir at room temperature overnight and the solvent was removed under reduced pressure. The crude product was stirred with ether, and the resulting solid (1.01 g, 84% yield) was collected by filtration. ¹ H NMR (300 MHz, DMSO) δ1.41 (s, 9H), 2.48 (br s, 4H), 3.46 (br s, 4H), 3.58 (d, J=18 Hz, 1H), 3.80 (d, J=18 Hz, 1H), 3.97 (br s, 1H), 4.03 (d, J=13 Hz, 1H), 4.24 (d, J=13 Hz, 1H), 5.20 (d, J=5 Hz, 1 H), 5.57 (s, 2H), 5.81 (dd, J=5, 8 Hz, 1H), 7.21-7.28 (m, 16H), 7.89 (d, J=7 Hz, 2H), 8.54 (d, J=6 Hz, 2H), and 9.30 (d, J=8, 1H).

E. 1- Piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium chloride

1- 2'-(1-acetyl-4-(t-butoxycarbonyl)piperazine)!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium chloride (1.01 g, 1 mmol) was dissolved in CH₂ Cl₂ (30 mL), and anisole (3.8 mL) and TFA (23 mL) were added sequentially. The solution was allowed to stir for 1 h at 0° C., and then was concentrated at reduced pressure. The crude reaction product was stirred with Et₂ O to produce a solid (0.483 g). This material was taken up in 1:1 MeOH/acetone (40 mL) and 2 eq of 1N HCl (1.1 mL) were added. The reaction was allowed to stir for 30 min at 0° C. before being concentrated at reduced pressure. The crude product was washed with EtOAc/Et₂ O and filtered to yield the title compound(0.483 g, 84% yield). ¹ H NMR (300 MHz, DMSO) δ3.07 (br s, 4H), 3.27 (br s, 4H), 3.59 (d, J=18, 1H), 3.77 (d, J=18, 1H), 3.91 (s, 2H), 4.38 (d, J=13, 1H), 4.44 (d, J=13, 1H), 5.14 (d, J=5, 1H), 5.58 (br s, 2H), 5.69 (dd, J=5,8, 2H), 7.23 (dd, J=2,9, 1H), 7.46 (m, 2H), 8.07 (d, J=7, 2H), 8.67 (d, J=7, 2H), and 9.30 (d, J=8, 1H); MS (FAB) m/e 668 (MH⁺); Anal. calcd for C₂₆ H₂₈ N₅ O₅ S₃ Cl₂.2HCl.3.5 H₂ O: C, 39.4; H, 4.5; N, 8.8. Found: C, 39.21; H, 4.38; N, 8.8.

EXAMPLE 2 1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido-!-5-thia-1-azabicyclo 4.2.0!oct-2-en-3-yl!methylthio!pyridinium chloride ##STR47## A. (6R)-trans-3-Chloromethyl-7- (2,5-dichlorophenyl)-thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylic acid

A slurry of (6R)-trans-3-chloromethyl-7- (2,5-dichlorophenyl)thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylate, diphenylmethyl ester (10.0 g, 15.8 mmol) in CH₂ Cl₂ (200 mL) at 0° C. was treated with anisole (24 mL) and then trifluoroacetic acid (80 mL). The resulting solution was stirred for 1 h at 0° C. and then concentrated under reduced pressure. The residue was stirred with Et₂ O, and the resulting solid was collected by filtration to give 5.20 g of (6R)-trans-3-chloromethyl-7- (2,5-dichlorophenyl)-thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylic acid as a white solid (70% yield), m.p. 125° C. ¹ H NMR (300 MHz, DMSO-d₆) δ3.51 (d, J=18 Hz, 1H), 3.70 (d, J=18 Hz, 1H), 3.91 (s, 2H), 4.52 (d, J=11 Hz, 1H), 4.58 (d, J=11 Hz, 1H), 5.13 (d, J=5 Hz, 1H), 5.70 (dd, J=5, 8 Hz, 1H), 7.24 (dd, J=2, 8 Hz, 1H), 7.47 (dd, J=2, 8 Hz, 2H), 9.28 (d, J=8 Hz, 1H).

B. 1- 2-Hydroxy-3-(t-butoxycarbonylamino)-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloropheylthio)acetamido!-5-thia-1- azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium chloride

1. Preparation of 1- N-(2-hydroxy-3-(t-butoxycarbonylamino)-1-propyl)-4-thiopyridone

To a solution of 4-thiopyrone (667 mg, 6.00 mmol) in 20 mL of ethanol was added 1-t-butoxycarbonylamino-3-aminopropan-2-ol (1.03 g, 5.40 mmol). This mixture was heated at reflux for 2 h under a nitrogen atmosphere. After cooling to rt, 30 mL of acetone was added and the solution was concentrated almost to dryness in vacuo. Acetone (20 mL) was added to the residue and the resulting solution was stored overnight (18 h) at -5° C. The precipitate which formed was collected by filtration to give 1.05 g (68%) of the title compound as an orange solid. ¹ H NMR (300 MHz, DMSO-d₆) δ1.37 (s, 9H), 2.94 (t, J=5, 2H), 3.66-3.77 (m, 2H), 4.03 (d, J=11, 1H), 5.33 (d, J=5, 1H), 6.86 (t, J=6, 1H), 7.12 (d, J=7, 2H), 7.52 (d, J=7, 2H); ¹³ C NMR (75 MHz) δ28.22, 43.75, 59.89, 68.84, 77.92, 129.65, 136.90, 155.73, 188.99; MS (DCI) m/e 285 (MH⁺). Anal. Calcd for C₁₃ H₂₀ N₂ O₃ S: C, 54.91;H, 7.09; N, 9.85. Found: C, 54.86; H, 7.18; N, 9.72.

2. Preparation of 1- 2-hydroxy-3-(t-butoxycarbonylamino)-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium chloride

To a solution of (6R)-trans-3-chloromethyl-7- (2,5-dichlorophenyl)thioacetamido!-8-oxo-5-thia-1-azabicyclo 4.2.0!oct-2-ene-2-carboxylic acid (793 mg, 1.70 mmol) in DMF (6 mL) was added 1- N- 2-hydroxy-3-(t-butixycarbonylamino)!-1-propyl!-4-thiopyridone (508 mg, 1.79 mmol). The mixture was stirred for 5 h. The DMF was removed in vacuo keeping the temperature below 30° C. The residue was stirred with ether until a powder was obtained. The solid was collected by filtration to give the crude product. This solid was stirred with ether for 2 h, and then collected by filtration to give 1.24 g (96%) of the title compound as a brown solid. ¹ H NMR (300 MHz, DMSO-d₆) δ1.37 (s, 9H), 3.04 (t, J=6, 2H), 3.50 (d, J=18, 1H), 3.74 (d, J=18, 1H), 3.81-3.83 (m, 1H), 3.91 (s, 2H), 4.25 (dd, J=9, 13, 1H), 4.34-4.43 (m, 2H), 4.58 (d, J=11, 1H), 5.13 (d, J=5, 1H), 5.67 (dd, J=5, 8, 1H), 6.98 (t, J=6, 1H), 7.22 (dd, J=2, 8.5, 1H), 7.43-7.47 (m, 2H), 8.00 (d, J=7, 2H), 8.71 (d, J=7, 2H), 9.30 (d, J=8, 1H); MS (FIA) m/e 715 (M⁺); Anal. calcd for C₂₉ H₃₂ N₄ O₇ S₃ Cl₂.HCl.0.5 H₂ O: C, 45.76; H, 4.50; N, 7.36. Found: C, 45.77; H, 4.72; 7.63.

C. 1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium chloride

A slurry of 1-(2-hydroxy-3-t-butoxycarbonylamino-1-propyl)-4- (6R)trans-2-carboxy-8-oxo-7- (2,5- dichlorophenylthio)acetamido!-5- thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium chloride (1.19 g, 1.58 mmol) in methylene chloride (22 mL) was cooled to 0° C. Anisole (3.4 mL) was added followed by trifluoroacetic acid (11 mL). The mixture was stirred for 30 min at 0° C. and 30 min at rt. The reaction mixture was concentrated in vacuo. The residue was stirred with ether until a yellow powder resulted. This solid was collected by filtration washing with ether. The crude product was stirred with ether (20 mL) for 45 min, and then the solid was collected by filtration. This was followed by similar treatments with acetone (1×10 mL) and then ether (1×20 mL). The final filtration gave 655 mg (54%) of the title compound as a yellow solid. ¹ H NMR (300 MHz, DMSO) δ2.80 (t, J=10, 1H), 3.06 (d, J=11, 1H), 3.31-3.44 (m, 1H), 3.60 (d, J=18, 1H), 3.90 (s, 2H), 4.10 (br s, 1H), 4.34-4.42 (m, 3H), 4.66 (d, J=12, 1H), 5.02 (d, J=5, 1H), 5.56 (t, J=6, 1H), 6.5-7.0 (br s, 1H), 7.21 (dd, J=2, 8, 1H), 7.41-7.46 (m, 2H), 8.12 (m, 2H), 8.30 (br s, 3H), 8.68 (m, 2H), 9.28 (m, 1H); MS (FIA) m/e 615 (MH⁺); Anal. calcd for C₂₄ H₂₄ N₄ O₅ S₃ Cl₂.HCl. HO₂ CCF₃ : C, 40.71; H, 3.55; N, 7.30. Found: C, 40.70; H, 3.52; 7.38.

The following compounds were prepared according to the general procedures of Examples 1 and 2 by varying the thiol starting material and the pyridine or thiopyridone derivative:

    __________________________________________________________________________      ##STR48##                                                                     Ex.                                                                            No.                                                                               Ar              R.sup.1  A            R.sup.2                                                                             R.sup.3                          __________________________________________________________________________      3 2,5-dichlorophenyl                                                                             NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.2                                                               H    H                                 4 2,6-dichloropyridin-4-yl                                                                       NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.2                                                               H    H                                 5 3-bromophenyl   NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.2                                                               H    H                                 6 2-chloro-5-trifluoromethylphenyl                                                               NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.2                                                               H    H                                 7 2-benzthiazolyl NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.2                                                               H    H                                 8 2,5-dimethylphenyl                                                                             NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.2                                                               H    H                                 9 2-bromopyrid-4-yl                                                                              NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.2                                                               H    H                                10 2,5-dichlorophenyl                                                                             NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.3                                                               H    H                                11 2,4,5-trichlorophenyl                                                                          NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.3                                                               H    H                                12 2,6-dichloropyrid-4-yl                                                                         NH.sub.2 CH.sub.2 CONH(CH.sub.2).sub.3                                                               H    H                                13 2,5-dichlorophenyl                                                                             NH.sub.2                                                                                 ##STR49##   H    H                                14 2,6-dichloropyrid-4-yl                                                                         NH.sub.2                                                                                 ##STR50##   H    H                                15 2,5-dichlorophenyl                                                                              ##STR51##                                                                              CH.sub.2 CO  H    H                                16 2,5-dichlorophenyl                                                                              ##STR52##                                                                              CH.sub.2 CONHCH.sub.2 CH.sub.2                                                              H    H                                17 2,5-dichlorophenyl                                                                             NH.sub.2 CH.sub.2 CH.sub.2                                                                           H    H                                18 2,4,5-trichlorophenyl                                                                          NH.sub.2 CH.sub.2 CH.sub.2                                                                           H    H                                19 2,6-dichloropyrid-4-yl                                                                         NH.sub.2 CH.sub.2 CH.sub.2                                                                           H    H                                20 2-chloro-5-trifluoromethylphenyl                                                               NH.sub.2 CH.sub.2 CH.sub.2                                                                           H    H                                21 2,5-dichlorophenyl                                                                             NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                22 2,4,5-trichlorophenyl                                                                          NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                23 2,6-dichloropyrid-4-yl                                                                         NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                24 2-chloro-5-trifluoromethylphenyl                                                               NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                25 2,5-dichloro-4-hydroxymethylphenyl                                                             NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                26 2,5-dichloro-4-hydroxyethylphenyl                                                              NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                27 2,5-dichlorophenyl                                                                             NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2                                                                  2-methyl                                                                            6-methyl                         28 2,5-dichlorophenyl                                                                             NH.sub.2                                                                                 ##STR53##   H    H                                29 2,6-dichloropyrid-4-yl                                                                         NH.sub.2                                                                                 ##STR54##   H    H                                30 2,5-dichlorophenyl                                                                             NHCH.sub.3                                                                              CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                31 2,5-dichlorophenyl                                                                             NHCH.sub.2 CH.sub.2 OH                                                                  CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                32 2,5-dichlorophenyl                                                                             N(CH.sub.3).sub.2                                                                       CH.sub.2 CH.sub.2 CH.sub.2                                                                  H    H                                33 2,5-dichlorophenyl                                                                              ##STR55##                                                                              CH.sub.2 CH.sub.2                                                                           H    H                                34 2,5-dichlorophenyl                                                                              ##STR56##                                                                               ##STR57##   H    H                                35 2,5-dichlorophenyl                                                                             NH.sub.2 (CH.sub.2).sub.4                                                                            H    H                                36 2,5-dichlorophenyl                                                                             NHCOO-t-Bu                                                                              (CH.sub.2).sub.4                                                                            H    H                                37 2,5-dichlorophenyl                                                                              ##STR58##                                                                              CH.sub.2 CH.sub.2                                                                           H    H                                38 2,5-dichlorophenyl                                                                              ##STR59##                                                                              (CH.sub.2).sub.4                                                                            H    H                                __________________________________________________________________________

                                      TABLE                                        __________________________________________________________________________     NMR DATA                                                                        ##STR60##                                                                     Comp.                                                Isolated                  of Ex. No.                                                                          H-2 H-6 H-7 H-3'                                                                               H-7'                                                                               NH     ArH    SPyrH  R      Form MS                   __________________________________________________________________________                                                               Data                  3   3.77(d,                                                                            5.16(d,                                                                            5.71(dd,                                                                           4.45(d,                                                                            3.93(s)                                                                            9.28(d, J=8)                                                                          3.48(dd, J=2,                                                                         8.75(d, J=7)                                                                          8.91(t, J=5)                                                                          HCl                                                                                 MH.sup.+ =642             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          8)     8.05(d, J=7)                                                                          8.10(br s)                            3.54(d,     4.38(d,        7.25(dd, J =2,                                                                               3.41(m)                               J=18)       J=13)          8)            2.91(m)                           4   3.70(d,                                                                            5.10(d,                                                                            5.63(dd,                                                                           4.51(d,                                                                            4.00(s)                                                                            9.31(d, J=8)                                                                          7.51(s)                                                                               8.63(d, J=7)                                                                          8.97(br s)                                                                            TFA                                                                                 MH.sup.+ =643             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)                 8.12(d, J=7)                                                                          7.97(br s)                            3.54(d,     4.38(d,                      5.27(s)                               J=18)       J=13)                        3.37(m)                                                                        2.91(m)                           5   3.76(d,                                                                            5.13(d,                                                                            5.67(dd,                                                                           4.43(d,                                                                            3.83d,                                                                             9.21(d, J=8)                                                                          7.54(t, J=2)                                                                          8.79(d, J=7)                                                                          9.01(t, J=5)                                                                          di                                                                                  MH.sup.+ =652             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)                                                                              J=15)      7.30-7.37(m)                                                                          8.05(d, J=7)                                                                          8.27(s)                                                                               Salt                           3.53(d,     4.36(d,                                                                            3.77(d,    7.23(t, J=8)  3.38-3.40(m)                          J=18)       J=13)                                                                              J=15)                    2.87-2.90(m)                      6   3.74(d,                                                                            5.13(d,                                                                            5.68(dd,                                                                           4.41(d,                                                                            3.96(s)                                                                            9.27(d, J=8)                                                                          7.55(s)                                                                               8.67(d, J=7)                                                                          8.80(br s)                                                                            di                                                                                  M.sup.+ =676              J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          7.54(d, J=8)                                                                          8.04(d, J=7)                                                                          7.92(br s)                                                                            Salt                           3.50(d,     4.37(d,        7.53(m)       5.26(s)                               J=18)       J=13)                        3.37(br s)                                                                     2.87(m)                           7   3.76(d,                                                                            5.15(d,                                                                            5.73(dd,                                                                           4.43(d,                                                                            4.22(s)                                                                            9.33(d, J=8)                                                                          7.99(d, J=8)                                                                          8.60(d, J=7)                                                                          8.98(s)                                                                               di                                                                                  M.sup.+ =631              J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          7.83(d, J=8)                                                                          8.07(d, J=7)                                                                          8.20(br s)                                                                            Salt                           3.54(d,     4.37(d,        7.44(t, J=7)  5.35(s)                               J=18)       J=13)          7.33(t, J=7)  3.37(br s)                                                                     2.90(br s)                        8   3.68(d,                                                                            5.09(d,                                                                            5.64(dd,                                                                           4.48(d,                                                                            3.71(s)                                                                            9.13(d, J=8)                                                                          7.11(s)                                                                               8.58(d, J=6)                                                                          8.82(br s)                                                                            di                                                                                  M.sup.+ =602              J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          7.04(d, J=8)                                                                          8.13(m)                                                                               7.82(br s)                                                                            Salt                           3.49(d,     4.38(d,        6.88(d, J=8)  5.22(s)                               J=18)       J=13)                        3.31(br s)                                                                     2.90(br s)                        9   3.76(d,                                                                            5.14(d,                                                                            5.68(dd,                                                                           4.42(d,                                                                            3.94(s)                                                                            8.32(d, J=8)                                                                          8.14(d, J=5)                                                                          8.71(d, J=7)                                                                          8.86(br s)                                                                            di                                                                                  M.sup.+ =653              J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          7.56(s)                                                                               8.03(d, J=5)                                                                          8.14(br s)                                                                            Salt                           3.53(d,     4.36(d,        7.33(d, J=4)  5.35(s)                               J=18)       J=13)                        3.39-3.32(m)                                                                   2.90(br s)                       10   3.75(d,                                                                            5.14(d,                                                                            5.69(dd,                                                                           4.43(d,                                                                            3.92(s)                                                                            9.31(d, J=8)                                                                          7.47(d, J=2)                                                                          8.71(d, J=7)                                                                          8.95(m)                                                                               di                                                                                  MH.sup.+ =656             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          7.46(d, J=8)                                                                          8.03(d, J=7)                                                                          8.12(m)                                                                               Salt                           3.53(d,     4.37(d,        7.24(dd, J=2, 5.32(br s)                            J=18)       J=13)          8)            3.19(m)                                                                        2.81(m)                                                                        1.76(m)                          11   3.75(d,                                                                            5.14(d,                                                                            5.69(dd,                                                                           4.43(d,                                                                            3.93(s)                                                                            9.28(d, J=8)                                                                          7.85(s)                                                                               8.65(d, J=7)                                                                          8.73(m)                                                                               HBr/TFA                                                                             MH.sup.+ =690             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          7.66(s)                                                                               8.03(d, J=7)                                                                          7.85(br s)                                                                            Salt                           3.52(d,     4.37(d,                      5.26(br s)                            J=18)       J=13)                        3.18(m)                                                                        2.82(m)                                                                        1.72(m)                          12   3.76(d,                                                                            5.14(d,                                                                            5.68(dd,                                                                           4.44(d,                                                                            4.00(s)                                                                            9.32(d, J=8)                                                                          7.51(s)                                                                               8.66(d, J=7)                                                                          8.74(t, J=5)                                                                          HBr/TFA                                                                             MH.sup.+ =657             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)                 8.03(d, J=7)                                                                          7.88(br s)                                                                            Salt                           3.53(d,     4.37(d,                      5.27(bs)                              J=18)       J=13)                        3.19(m)                                                                        2.83(m)                                                                        1.73(m)                          14   3.70(d,                                                                            5.12(d,                                                                            5.66(dd,                                                                           4.44(d,                                                                            4.00(s)                                                                            9.28(d, J=8)                                                                          7.50(s)                                                                               8.62(d, J=7)                                                                          8.70(m)                                                                               HBr/TFA                                                                             M.sup.+ =673              J=18)                                                                              J=5)                                                                               J, 5, 8)                                                                           J=12)                 8.06(d, J=7)                                                                          5.25(s)                                                                               Salt                           3.50(d,     4.38(d,                      3.76(m)                               J=18)       J=12)                        3.19(m)                                                                        2.66-2.89(m)                     13   3.74(d,                                                                            5.14(d,                                                                            5.68(dd,                                                                           4.43(d,                                                                            3.90(s)                                                                            9.26(d, J=8)                                                                          7.46(m)                                                                               8.62(d, J=7)                                                                          8.70(m)                                                                               HBr/TFA                                                                             M.sup.+ =672              J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=12)          7.23(m)                                                                               8.03(d, J=7)                                                                          5.24(s)                                                                               Salt                           3.51(d,     4.36(d,                      3.77(m)                               J=18)       J=12)                        2.87(m)                                                                        2.71(m)                          15   3.77(d,                                                                            5.14(d,                                                                            5.69(dd,                                                                           4.44(d,                                                                            3.91(s)                                                                            9.30(d, J=8)                                                                          7.23(dd, J=2,                                                                         8.67(d, J=7)                                                                          5.58(br s)                                                                            di                                                                                  MH.sup.+ =668             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=13)          9)     8.07(d, J=7)                                                                          3.27(br s)                                                                            salt                           3.59(d,     4.38(d,        7.46(m)       3.07(br s)                            J=18)       J=13)                                                         16   3.70(d,                                                                            5.09(d,                                                                            5.63(dd,                                                                           4.45(s)                                                                            3.90(s)                                                                            9.23(d, J=8)                                                                          7.46(dd, J=2,                                                                         8.56(d, J=7)                                                                          5.20(s)                                                                               TFA                                                                                 M.sup.+ =684              J=18)                                                                              J=5)                                                                               J=5, 8)            9)     8.05(d, J=7)                                                                          3.26(m)                               3.47(d,                    7.23(dd, J=2,                                       J=18)                      8)                                             17   3.76(d,                                                                            5.15(d,                                                                            5.68(dd,                                                                           4.40(s)                                                                            3.93(s)                                                                            9.32(d, J=8)                                                                          7.47(m)                                                                               8.88(d, J=7)                                                                          8.46(m)                                                                               di                                                                                  MH.sup.+ =585             J=18)                                                                              J=5)                                                                               J=5, 8)            7.24(dd, J=2,                                                                         8.07(d, J=7)                                                                          4.82(m)                                                                               salt                           3.50(d,                    8)            3.44(m)                               J=18)                                                                     18   3.76(d,                                                                            5.14(d,                                                                            5.68(dd,                                                                           4.40(s)                                                                            3.95(s)                                                                            9.33(d, J=8)                                                                          7.85(s)                                                                               8.90(d, J=7)                                                                          8.71(m)                                                                               di                                                                                  MH.sup.+ =618             J=18)                                                                              J=5)                                                                               J=5, 8)            7.67(s)                                                                               8.07(d, J=7)                                                                          4.83(m)                                                                               salt                           3.50(d,                                  3.40(m)                               J=18)                                                                     19   3.77(d,                                                                            5.15(d,                                                                            5.69(dd,                                                                           4.41(s)                                                                            4.02(s)                                                                            9.33(d, J=8)                                                                          7.52(s)                                                                               8.84(d, J=7)                                                                          8.51(s)                                                                               di                                                                                  MH.sup.+ =586             J=18)                                                                              J=5)                                                                               J=5, 8)                   8.07(d, J=7)                                                                          4.79(t, J=6)                                                                          salt                           3.50(d,                                  3.44(m)                               J=18)                                                                     20   3.75(d,                                                                            5.70(dd,                                                                           5.15(dd,                                                                           4.45(d,                                                                            4.00(s)                                                                            9.28(d, J=8)                                                                          7.81(s)                                                                               8.76(d, J=7)                                                                          4.72(m)                                                                               HCl/TFA                                                                             MH.sup.+ =619             J=18)                                                                              J=5, 8)                                                                            J=5, 8)                                                                            J=13)          7.71(d, J=8)                                                                          8.12(d, J=7)                                                                          3.48(m)                                                                               Salt                           3.48(d,     4.38(d,        7.56(d, J=8)                                        J=18)       J=13)                                                         21   3.72(d,                                                                            5.12(d,                                                                            5.67(d,                                                                            4.41                                                                               3.42(s)                                                                            9.25(d, J=8)                                                                          7.49(d, J=2)                                                                          8.76(d, J=7)                                                                          7.42(br s)                                                                            HCl/TFA                                                                             MH.sup.+ =599             J=18)                                                                              J=5)                                                                               J=5)                                                                               (br s)         7.48(d, J=8)                                                                          8.07(d, J=7)                                                                          4.50(t, J=7)                                                                          Salt                           3.48(d,                    7.25(dd, J=2, 2.83(m)                               J=18)                      8)            2.15(m)                          22   3.71(d,                                                                            5.12(d,                                                                            5.68(dd,                                                                           4.40                                                                               3.94(s)                                                                            9.26(d, J=8)                                                                          7.86(s)                                                                               8.75(d, J=7)                                                                          7.88(br s)                                                                            di                                                                                  MH.sup.+ =634             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            (br s)         7.68(s)                                                                               8.07(d, J=7)                                                                          4.49(t, J=7)                                                                          Salt                           3.48(d,                                  2.83(m)                               J=18)                                    2.15(m)                          23   3.75(d,                                                                            5.14(d,                                                                            5.69(dd,                                                                           4.39                                                                               4.01(s)                                                                            9.29(d, J=8)                                                                          7.52(s)                                                                               8.76(d, J=7)                                                                          7.90(br s)                                                                            HCl/TFA                                                                             MH.sup.+ =600             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            (br s)                8.05(d, J=7)                                                                          4.50(t, J=7)                                                                          Salt                           3.49(d,                                  2.85(m)                               J=18)                                    2.15(m)                          24   3.70(d,                                                                            5.11(d,                                                                            5.66(dd,                                                                           4.42(d,                                                                            3.97(s)                                                                            9.28(d, J=8)                                                                          7.78(s)                                                                               8.76(d, J=7)                                                                          8.06(br s)                                                                            HCl/TFA                                                                             MH.sup.+ =633             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            J=15)          7.69(d, J=8)                                                                          8.07(d, J=7)                                                                          4.50(t, J=7)                                                                          Salt                           3.45(d,     4.36(d,        7.53(d, J=8)  2.83(m)                               J=18)       J=15)                        2.15(m)                          25   3.74(d,                                                                            5.13(d,                                                                            5.68(dd,                                                                           4.32-                                                                              3.89(s)                                                                            9.26(d, J=8)                                                                          4.47(s)                                                                               8.83(d, J=7)                                                                          8.14(br s)                                                                            di/TFA                                                                              M.sup.+ =629              J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            4.42(m)        7.51(s)                                                                               8.04(d, J=7)                                                                          4.50-4.61(m)                                                                          Salt                           3.45(d,                    7.46(s)       2.76-2.93(m)                          J=18)                                    3.12-2.24(m)                     26   3.70(d,                                                                            5.09(d,                                                                            5.63(dd,                                                                           4.39                                                                               3.86(s)                                                                            9.23(d, J=8)                                                                          7.46(s)                                                                               8.77(d, J=7)                                                                          7.90(br s)                                                                            di/TFA                                                                              MH.sup.+ =643             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            (br s)         7.44(s)                                                                               8.08(d, J=7)                                                                          4.50-4.52(m)                                                                          Salt                           3.42(d,                                  4.62-4.75(m)                          J=18)                                    3.55(br s)                                                                     2.13(br s)                                                                     2.77(t, J=6)                     27   3.65(d,                                                                            5.04(d,                                                                            5.59(dd,                                                                           4.38                                                                               3.91(s)                                                                            9.28(d, J=8)                                                                          7.56(d, J=2)                                                                          8.63(d, J=7)                                                                          8.05-8.25(br                                                                          HCl/TFA                                                                             MH.sup.+ =701             J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            (br s)         7.46(d, J=8)                                                                          8.14(d, J=7)                                                                          4.62(s)                                                                               Salt                           3.43(d,                    7.22(dd, J=2, 4.38(m)                               J=18)                      8)            3.02-3.18(m)                                                                   2.86-3.01(m)                                                                   2.04-2.18(m)                                                                   1.19(t, J=7)                     28   3.60(d,                                                                            5.02(d,                                                                            5.56(t,                                                                            4.34-                                                                              3.90(s)                                                                            9.28(t, J=7)                                                                          7.41-7.46(m)                                                                          8.68(t, J=8)                                                                          8.30(br s)                                                                            HCl/TFA                                                                             MH.sup.+ =615             J=18)                                                                              J=5)                                                                               J=6)                                                                               4.42(m         7.21(dd, J=2,                                                                         8.12(t, J=8)                                                                          6.5-7.0(br                                                                            Salt                           3.31-       overlaps       8)            4.66(d, J=12)                         3.44(m)     with R)                      4.34-4.42(m                                                                    overlaps with                                                                  R)                                                                             4.10(br, s)                                                                    3.06(d, J=11)                                                                  2.80(t, J=10)                    29   3.63(d,                                                                            5.04(d,                                                                            5.55-                                                                              4.40                                                                               4.03(d,                                                                            9.36(d, J=5)                                                                          7.48(s)                                                                               8.08(bs)                                                                              8.29(br s)                                                                            HCl/TFA                                                                             MH.sup.+ =618             J=18)                                                                              J=5)                                                                               5.60(m)                                                                            (br s)                                                                             J=16)             8.67(bs)                                                                              4.67(d, J=12)                                                                         Salt                           3.42(d,         3.97(d,                  4.40(br s,                            J=18)           J=16)                    overlaps with                                                                  H-3)                                                                           4.11(br s)                                                                     3.07(d, J=11)                                                                  2.80(m)                          30   3.62(d,                                                                            5.02(d,                                                                            5.60-                                                                              4.38(m)                                                                            3.90(s)                                                                            9.25(br s)                                                                            7.45(m)                                                                               8.70(d, J=7)                                                                          2.75(m)                                                                               HCl                                                                                 MH.sup.+ =613             J=18)                                                                              J=5)                                                                               5.62(m)            7.21(m)                                                                               8.16(d, J=7)                                                                          2.54(s)                               3.40(d,                                  4.40(m)                               J=18)                                                                     31   3.50(d,                                                                            4.93(d,                                                                            5.45(dd,                                                                           4.48(m)                                                                            3.92(s)                                                                            9.36(d, J=8)                                                                          7.45(m)                                                                               8.70(d, J=7)                                                                          4.48(m)                                                                               HCl                                                                                 MH.sup.+ =642             J=18)                                                                              J=5)                                                                               J=5, 8)            7.19(d, J=8)                                                                          8.16(d, J=7)                                                                          3.58(m)                               3.30(d,                                  2.86(m)                               J=18)                                    2.19(m)                          32   3.59(d,                                                                            5.01(d,                                                                            5.55-                                                                              4.45(m)                                                                            3.92(m)                                                                            9.37(d, J=6)                                                                          7.42(m)                                                                               8.73(br s)                                                                            2.20(m)                                                                               HCl                                                                                 M.sup.+ =627              J=18)                                                                              J=5)                                                                               5.60(m)            7.18(m)                                                                               8.16(br, s)                                                                           2.52(s)                               3.20(d,                                  4.42(m)                               J=18)                                                                     33   3.78(d,                                                                            5.17(d,                                                                            5.72(dd,                                                                           4.42                                                                               3.95(s)                                                                            9.30(d, J=8)                                                                          7.48(m)                                                                               8.78(d, J=7)                                                                          4.64(m)                                                                               HCl                                                                                 M.sup.+ =655              J=18)                                                                              J=5)                                                                               J=5, 8)                                                                            (br s)         7.26(dd, J=2,                                                                         8.04(d, J=7)                                                                          3.57(br s)                            3.54(d,                    8)            2.90(m)                               J=18)                                    2.52(m)                          34   3.68(d,                                                                            5.11(d,                                                                            5.65(dd,                                                                           4.40(s)                                                                            3.92(s)                                                                            9.29(d, J=8)                                                                          7.46(m)                                                                               8.70(d, J=7)                                                                          4.63(m)                                                                               HCl                                                                                 MH.sup.+ =685             J=18)                                                                              J=5)                                                                               J=5, 8)            7.23(m)                                                                               8.03(d, J=7)                                                                          4.36(m)                               3.49(d,                                  4.14(m)                               J=18)                                    2.66(m)                                                                        2.57(m)                          35   3.74(d,                                                                            5.13(d,                                                                            5.69(dd,                                                                           4.37(s)                                                                            3.91(s)                                                                            9.27(d, J=18)                                                                         7.47(m)                                                                               8.77(d, J=7)                                                                          4.42(m)                                                                               HCl/TFA                                                                             M.sup.+ =613              J=18)                                                                              J=5)                                                                               J=5, 8)            7.25(m)                                                                               8.04(d, J=7)                                                                          2.79(m)                                                                               Salt                           3.49(d,                                  1.89(m)                               J=18)                                    1.51(m)                          36   3.48(d,                                                                            5.13(d,                                                                            5.68(dd,                                                                           4.32(m)                                                                            3.91(s)                                                                            9.28(d, J=8)                                                                          7.46(m)                                                                               8.78(d, J=7)                                                                          4.40(m)                                                                               HCl                                                                                 M.sup.+ =713              J=18)                                                                              J=5)                                                                               J=5, 8)     6.87(t, J=6)                                                                          7.23(m)                                                                               8.02(d, J=7)                                                                          2.92(m)                               3.49(d,                                  1.81(m)                               J=18)                                    1.34(m)                                                                        1.34(s)                          37   3.71(d,                                                                            5.10(d,                                                                            5.65(dd,                                                                           4.36(m)                                                                            3.90(s)                                                                            9.24(d, J=8)                                                                          7.46(dd, J=2,                                                                         8.70(d, J=7)                                                                          4.52(m)                                                                               TFA                                                                                 MH.sup.+ =629             J=18)                                                                              J=5)                                                                               J=5, 8)            8)     8.06(d, J=7)                                                                          3.67(m)                               3.45(d,                    7.22(dd, J=2,                                       J=18)                      8)                                             38   3.74(d,                                                                            5.12(d,                                                                            5.67(dd,                                                                           4.39(s)                                                                            3.92(s)                                                                            9.31(d, J=8)                                                                          7.45(m)                                                                               8.86(d, J=7)                                                                          8.08((m)                                                                              di                                                                                  M.sup.+ =655              J=18)                                                                              J=5)                                                                               J=5, 8)            7.22(dd, J=2,                                                                         8.03(d, J=7)                                                                          7.27(m)                                                                               Salt                           3.50(d,                    8)            4.50(m)                               J=18)                                    3.1-3.17(m)                                                                    1.91(m)                                                                        1.45-1.56(m)                     __________________________________________________________________________ 

We claim:
 1. A compound having the formula ##STR61## wherein Ar is a group selected from ##STR62## in which R⁴, R⁵ and R⁶ are each independently hydrogen, halogen, trihalomethyl, amino, hydroxy, hydroxy(C₁ -C₆)alkyl, C₁ -C₆ alkyl, --(CH₂)_(n) OR⁷ or --(CH₂)_(n) SR⁷ ; n is an integer of from 1 to 6; R⁷ is hydrogen or C₁ -C₆ alkyl; R¹ represents a group of the formula ##STR63## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl or (C₁ -C₆)alkoxycarbonyl, said C₁ -C₆ group being optionally substituted by one or more hydroxy or C₁ -C₆ alkoxy groups; m is either 0 or 1; A is a C₂ -C₁₀ alkyl group optionally substituted by 1 to 5 hydroxy groups; R² and R³ are each independently hydrogen or C₁ -C₆ alkyl; and R¹⁰ is hydrogen, an anionic charge or a carboxyl-protecting group, provided that when R¹⁰ is hydrogen or a protecting group, there is also present a counter ion; or a pharmaceutically acceptable salt or prodrug thereof.
 2. A compound of claim 1 wherein R¹ is ##STR64## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl, hydroxy(C₁ -C₆) alkyl or (C₁ -C₆)alkoxycarbonyl and A is a C₂ -C₁₀ alkyl group optionally substituted by 1-5 hydroxy groups.
 3. A compound of claim 2 wherein R¹ is ##STR65##
 4. A compound of claim 1, claim 2 or claim 3 wherein Ar is ##STR66## in which R⁴, R⁵ and R⁶ are each independently hydrogen, C₁ -C₆ alkyl, halogen, trifluoromethyl, hydroxy or hydroxy(C₁ -C₆)alkyl.
 5. A pharmaceutical composition comprising an effective antibacterial amount of a compound of claim 1 and a pharmaceutically acceptable carrier or excipient.
 6. A method of treating a bacterial infection which comprises administering to a host afflicted with such infection an effective antibacterial amount of a compound of claim
 1. 7. A method of treating a bacterial infection caused by a strain of methicillin-resistant Staphylococcus aureus which comprises administering to a host afflicted with such infection an effective antibacterial amount of a compound of claim
 1. 8. A compound having the formula ##STR67## wherein Ar is a group selected from ##STR68## in which R⁴, R⁵ and R⁶ are each independently hydrogen, halogen, trihalomethyl, amino, hydroxy, hydroxy(C₁ -C₆)alkyl, C₁ -C₆ alkyl, --(CH₂)_(n) OR⁷ or --(CH₂)_(n) SR⁷ ; n is an integer of from 1 to 6; R⁷ is hydrogen or C₁ -C₆ alkyl; R¹ represents a group of the formula ##STR69## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl or (C₁ -C₆)alkoxycarbonyl, said C₁ -C₆ alkyl group being unsubstituted or substituted by 1 or 2 hydroxy or C₁ -C₆ alkoxy groups; m is either 0 or 1; A is a C₂ -C₁₀ alkyl group or a C₂ -C₁₀ alkyl group substituted by 1-5 hydroxy groups; R² and R³ are each independently hydrogen or C₁ -C₆ alkyl; and R¹⁰ is hydrogen, an anionic charge or a carboxyl-protecting group, provided that when R¹⁰ is hydrogen or a carboxyl-protecting group, there is also present a counter ion; or a pharmaceutically acceptable salt or prodrug thereof.
 9. A compound of claim 8 wherein R¹ is ##STR70## in which R⁸ and R⁹ are each independently hydrogen, C₁ -C₆ alkyl, hydroxy(C₁ -C₆)alkyl or (C₁ -C₆)alkoxycarbonyl.
 10. A compound of claim 9 wherein R¹ is ##STR71##
 11. A compound according to claim 8, 9 or 10 wherein Ar is ##STR72## in which R⁴, R⁵ and R⁶ are each independently hydrogen, C₁ -C₆ alkyl, halogen, trifluoromethyl, hydroxy or hydroxy(C₁ -C₆)alkyl.
 12. A compound selected from the group consisting of1- Piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (3-bromophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-benzthiazolylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dimethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-bromopyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-2-hydroxy-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-2-hydroxy-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-guanidinyl-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-hydroxymethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-(2-hydroxy-1-ethyl)phenylthio))acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-1-propyl)-2,6-dimethyl-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-methylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-(2-hydroxyethyl)-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-dimethylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-(N-morpholinyl)-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-(N-morpholinyl)-2-hydroxy-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7-(2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 4-amino-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 4-(t-butoxycarbonylamino)-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(2-guanidinyl-1-ethyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; and 1-(4-guanidinyl-1-butyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof.
 13. A compound selected from the group consisting of1- Piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (3-bromophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dimethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-bromopyrid-4-ylthio) acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- IN-(3-amino-2-hydroxy-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-guanidinyl-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-hydroxymethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-(2-hydroxy-1-ethyl)phenylthio))acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-1-propyl)-2,6-dimethyl-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-(2-hydroxyethyl)-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-dimethylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 4-amino-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 4-(t-butoxycarbonylamino)-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; and 1-(2-guanidinyl-1-ethyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; and 1-(4-guanidinyl-1-butyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof.
 14. A compound selected from the group consisting of1- Piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(2-Hydroxy-3-amino-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (3-bromophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dimethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-amino-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-bromopyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(3-amino-1-propyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; - piperazinylcarbonylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- N-(2-guanidinyl-1-ethyl)carbamoylmethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 2-amino-1-ethyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,4,5-trichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,6-dichloropyrid-4-ylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2-chloro-5-trifluoromethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-amino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichloro-4-hydroxymethylphenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-1-propyl)-2,6-dimethyl-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(3-amino-2-hydroxy-1-propyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 3-dimethylamino-1-propyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 4-amino-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1- 4-(t-butoxycarbonylamino)-1-butyl!-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; 1-(2-guanidinyl-1-ethyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof; and 1-(4-guanidinyl-1-butyl)-4- (6R)-trans-2-carboxy-8-oxo-7- (2,5-dichlorophenylthio)acetamido!-5-thia-1-azabicyclo 4.2.0!-oct-2-en-3-yl!methylthio!pyridinium inner salt or a pharmaceutically acceptable salt or prodrug thereof.
 15. The compound of the formula ##STR73## or a pharmaceutically acceptable salt or prodrug thereof.
 16. A pharmaceutical composition comprising an effective antibacterial amount of a compound of claim 15 and a pharmaceutically acceptable carrier or excipient.
 17. A method of treating a bacterial infection which comprises administering to a host afflicted with such infection an effective antibacterial amount of a compound of claim
 15. 18. A method of treating a bacterial infection caused by a strain of methicillin-resistant Staphylococcus aureus which comprises administering to a host afflicted with such infection an effective antibacterial amount of a compound of claim
 15. 